Patent GB-1044002-A (GB)
Title: Improvements in or relating to visual indicating systems for aircraft
Inventor: MAJENDIE ALASTAIR MICHAEL ADAI
IPC: B64D45/00
Filed: 1962-05-22
Abstract: 1,044,002. Aircraft instruments. SMITHS INDUSTRIES Ltd. May 16, 1963 [May 22, 1962], No. 19599/62. Addition to 853,034. Heading B7W. An aircraft instrument comprises an indicator producing a moving optical stimulus at or near the periphery of the pilot's normal field of vision, and computer means responsive to aircraft height, pitch angle, and elevator setting angle signals to produce a signal demanding the pitch changes required during the flare phase of landing, the indicator responding to the sense and magnitude of the signal from the computer. In Fig. 1, the indicator 1, 2, 3 is as described in Specification 853,034, and is energized by amplifier 9 and motor 8, a tachometer generator 10 providing a feedback signal to a summing network 11 so that the speed and direction of rotation of cylinder 1 represent the magnitude and sense of the output of network 110. Inputs to the computer are provided by a radio altimeter 12, glide-path receiver 13, vertical gyro 14, and elevator setting transducer 49. Further, the pilot sets a datum height hd on a potentiometer 31, being the level to which the flare phase flight path is to be asymptotic (e.g. between + 10 ft. and - 10 ft.), sets an altitude height on a potentiometer device 32, being the height above the set datum at which flight along a glide-path beam is replaced by flight along an extrapolation of the beam (e.g. betweeen 100 and 300 ft.), and sets a flare height on a potentiometer device 40, being the height above the set datum at which the flare phase begins (e.g. between 50 and 150 ft., but less than the altitude height). Initially, all relays are de-energized, and their contacts are as shown. When flying an ILS approach, the pilot closes switch ILS, energizing relay FP from a D.C. source at terminal 20. This changes over contact FP1, and connects a trigger amplifier 30 to'the gate of a silicon-controlled rectifier 33. While the h signal from altimeter 12 is greater than the altitude height derived from potentiometers 31 and 32, the output of amplifier 30 is zero, the diode 33 does not conduct, and relay A is unenergized. The sole input to network 111 is from the glide phase computer 26, which derives a signal (#-K 11 #)-#/(1+# 4 D) where # is the pitch angle, # is the angular displacement of the aircraft from the glide-path, K 11  is a constant, and # 4  is, say, thirty seconds. This is the only input to a summing amplifier 27, which passes the signal through a network 28 having a transfer function f 1 (D) equal to (1+N# 1 D)/ (1+# 1 D) where N is between one and eight, and # 1  is not more than a fifth of a second. The resultant signal controls the indicator 1, which appears as forwardly moving light sources when a nose-down correction is demanded, and rearwardly moving sources for a nose-up correction. When the measured height goes below the altitude height set on potentiometers 31 and 32, amplifier 30 delivers a signal to diode 33. Terminal 29 is supplied with a positive half-wave rectified A.C. voltage, so that the diode is triggered and energizes relay A, which holds itself on through contacts A1. Contact A2 changes over, but relay F is delayed in operation by capacitor 36. Contact A3 is changed over, so that amplifier 30 will now have an output only when the aircraft descends to the flare height set on potentiometer 40. Diode 33 is therefore not triggered when the next half-wave appears at terminal 29, and relay F does not become energized, but will become energized when amplifier 30 next produces an output signal. The changeover of contact A4 removes the glide path signal from network 27, and substitutes a pitchdeviation signal # - #d produced by an electromechanical integrator 47 described in Fig. 3 (not shown). While relay A is de-energized, integrator 47 computes the average pitch angle #d during the glide-path phase. When relay A is energized, it thereafter computes # - #d, which is therefore passed to network 110 as K 1 f 1 (D)(# - #d) by network 28, K 1  being a constant. Further, contact A6 is changed over, so that an elevator setting signal # is passed through network 111 having a transfer function f 2 (D) equal to # 2 D/(1+# 2 D), so that the input to network 11 is now K 1 f 1 (D)(# - #d)- GK 6 K 7 f 2 (D)# where G, K 6 , and K, are constants. This serves to hold the pitch altitude constant during the second landing phase. The end of this phase occurs when the measured height above the set datum goes below the height set on potentiometer 40, so that amplifier 30 supplies a trigger signal to diode 33, which conducts to energize relay F. Contact F4 changes over so that relay G is also energized. Contacts F2 and G1 change over, so that network 27 has an input from network 48, which operates on its h - hd input by a transfer function 1+ K 5 D where K 5  is between four and eight seconds. Contact G2 also changes over, so that the signal from integrator 47 passes through a network 50 having a transfer function f 2 (D) like network 111, to produce a signal K 6 K 7 f 2 (D)#. The input to network 111 is unchanged. The inputs to network 110 thus represent K 6 f 1 (D)[(1+K 5 D) (h-hd)+-K 7 f 2 (D)#]-GK 6 K 7 f 2 (D) # . An alternative function may be selected during the flare phase, by manual opening of contacts CL1 and CL2. The former de-energizes relay G, and the latter removes the input to network 111, since contact F5 is changed over during the flare phase. Contact G1 remains as shown, so that the signal from network 48 is passed through integrator 280 having transfer function 1/K 4 D. Contact G2 is also as shown, cutting out network 50. The total input to network 110 is therefore K 2 f 1 (D)[(# - #d)+K 3  (1+1/K 4 D)(h-hd)] where K 2  and K 3  are constants and K 4  is, say, four seconds. In some cases, a nose-down demand, is made when the flare phase begins, which is not always desirable. To minimize this, change over of contact F1 momentarily energizes relay P through capacitor 42. This changes over contacts P1 and P2, the former energizing relay FD, and the latter charging capacitor 54 which holds relay FD on for, say, two seconds after contacts P1 and P2 revert to the position shown. The contacts FD1 and FD2 change over, substituting a delay network 56, 58, 59, for network 28, a diode 57 ensuring that nosedown signals only are delayed, and thus not presented unless large or persistent. During ground controlled approach, the pilot leaves switch ILS open, and closes switches GCA1 and GCA2. The latter is equivalent to switch ILS, so that the above described computations occur, and the former switch energizes relay G, changing over contact G3, so that during the approach, a shutter device 15 is de-energized so that the indicator is masked. During the flare phase however, contact F3 energizes the shutter device so that the indicator is visible.